Either PRP or HA is each effective for treating knee OA. However, the efficacy of combined PRP and HA injections remains unknown clinically.

Intraarticular plasma-rich platelet (PRP) or hyaluronic acid (HA) was each effective for knee osteoarthritis(OA). The efficacy of combined injections remains unknown. This study aimed to evaluate the efficacy of PRP combined with different hyaluronan for treating knee OA. In a prospective, randomized-controlled trial, 95 patients with Kellgren-Lawrence grade 2 knee OA were randomized to receive a single intraarticular Artz (10mg/ml) followed by PRP (N=48) into target knee or single HYAJOINT Plus (20mg/ml) injection followed by PRP (N=47). Primary outcome was the change from baseline in the visual analog scale (VAS) pain at 6 months. Secondary outcomes included the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Lequesne index, single leg stance test (SLS), use of rescue analgesics and patient satisfaction.

Inclusion Criteria:

• Age of 20-85 years Symptomatic knee osteoarthritis for more than 6 months despite analgesics, NSAIDs, or physical therapy Kellgren-Lawrence grade-2 knee osteoarthritis seen on radiographs made within previous 6 months Radiological evidence of bilateral knee OA was accepted if global pain VAS in the contralateral knee was less than 30 mm.

Exclusion Criteria:

• Previous orthopedic surgery on spine or lower limb Disabling osteoarthritis of either hip or foot Knee instability, apparent joint effusion, or marked valgus/varus deformity Known allergy to avian proteins or hyaluronan products Confirmed or suspected pregnancy, or lactating Intra-articular injections into knee in previous 6 months Any specific medical conditions (rheumatoid arthritis, active infection, hemiparesis, neoplasm, hematological etc.) that would interfere with assessments

One of the investigator, blinded to the allocation groups, performed all the assessments. The patients were blinded, by preventing visual access to the injection field with a screen placed between them and their knee during the injection process. They were not informed of which HA they had received during the study period.